This invention relates generally to current limiters, and more particularly to a current limiter having coaxial contacts which are spring loaded against one another and which, when opened, form an arcing chamber, the walls of which may emit a gas.
One known current limiter device which utilizes a current-carrying spring to provide contact pressure for a pair of axially aligned contacts is shown in Swiss Pat. No. 566 640. The current-carrying spring additionally functions as an electrodynamic drive for opening the contacts. Thus, if the current through the spring exceeds a predetermined level, the spring contracts by operation of magnetic forces which are produced within the spring. Such contraction causes the axially aligned contacts to open. As the contacts are open, an arc is produced which causes the walls of a chamber in which the contacts are disposed to emit a gas. Such an emission of gas increases the pressure in the chamber. The combination of the increased pressure in the chamber and the increased distance between the contacts causes an increase in the voltage required to maintain the arc, thereby limiting the current through the spring. After the contacts have been separated by a predetermined distance, discharge openings are exposed which permit the pressurized gas to flow into a chamber having a volume larger than the arc chamber, and which is provided with discharge openings for the gas. This embodiment, however, has the disadvantage that the fabrication and design of the compression spring which must carry a predetermined current corresponding to the current rating of the device is complex and expensive.
It is, therefore, an object of this invention to improve current limiting devices.
It is a further object of this invention to provide an improved current limiting device which is inexpensive and is simple to manufacture.
It is another object of this invention to provide a current limiting device which does not unduly stress a mechanical structure as the contacts are opened.